The objective is to shed light upon cases of cutaneous malignant melanoma (CMM) by means of a molecular epidemiology case-control investigation, with the hope of developing primary prevention measures against the steadily increasing occurrence of this tumor. The study is planned specifically to investigate the individual and combined influence of sun exposure and DNA repair proficiency on melanoma risk. The study site in Italy has been chosen because of its particular characteristics: highly prevalent sun exposure, a very large population served by a single hospital, and therein a highly experienced dermatology division which can ensure excellency in case identification. Pilot investigations guarantee a minimal accrual rate per year of 50 cases of stage I CMM and 50 controls, matched by age and gender, for a three year period. Controls are sought among cases for possible confounders. Privileged attention will be devoted to dose-response models. As secondary hypotheses, the association of DNA repair proficiency decline with loss of heterozygosity of chromosome 1p and 9p, with UV-specific ras gene mutations, and with p53 gene overexpression will be studied among cases. The study project and the informed consent form have been approved by the IRB of the University of Milan, the Bufalini Hospital in Cesna, and the Institute Clinici di Perfezionamento in Milan.